Conversion of pinene compounds into isobornyl ester and camphene mixture



UNITED STATES PATENT OFFICE.

LAURENCE G. WESSON, 0F CHEVY CHASE, MARYLAND.

CONVERSION OF PINE-NE COMPOUNDS INTO ISOBORNYL ESTER AND GAIMPHENEMIXTURE.

No Drawing.

To all whom it may concern:

Be it lmown that I, LAURENCE G. WassoN, a citizen of the United Statesof America, residing at Chevy Chase, in the county of Montgomery andState of Maryland, have invented certain new and useful Im provements inConversion of Pinene Comounds into Isobornyl Ester and Qamphene ixture,of which the following is a spoolfication.

The present invention pertains to the conversion of pinene hydrohaloidsinto other hydrocarbon derivatives suitable for use 1n the preparationof camphor and for analogous uses.

Among the objects of the invention is the acceleration of thetransformation of the pinene group into the camphene or isobornyl group,by isomerization, andthe performance of this reaction withthe use of aminimum amount of chemicals, andwhile making possible the recovery of asubstantial fraction (from 50 to 75%) of the HCl component of the pinenehydro'chlorid, preferably used as starting material.

The mostimportant object, however, is the 'reduction' in the amount ofresinous products produced during the transformation, as compared withthe amounts ordi-- narily obtained by the use of zinc salts or of zinc.

These and other objects, whichpwill be obvious from the description, aresecured by the use of the novel procedure hereinbelow set forth.

In accordance with the process of the present invention, a mixture ofpinene hydro-.

chlorid and glacial acetic acid is heated. to-

gether with a small amount of metalliczinc,

the latter being used in the form of a coarse powder, granulated zinc orother-relatively pletion of the reaction.

coarse pieces, in place of the morefinely d1 vided zinc dust. Thereaction. is carriedout by heating the mixture-ofjacetic acid and ingsay about 120 C.,), and maintaining the mixture actively .boiling untilthe com-.

- To more fully explain the invention, I" give the following example,the same-being for the purpose .ofillustrating specific procedarefalling within the scope of the in- .Se uent run of the process.

inene hydrochlorid to vigorous boil Specification of Letters Patent.Patented Mar, 22, 1921,

Application filed June 30, 1919. Serial No. 307,762.

ventio-n, but the invention is not to be understood as limited thereto.

P nene hydrochlorid is mixed with glacial acetic ac d, in theproportions, respectively, Of about 100 to 300 parts, by weight. 5 partsor less (2 parts ordinarily being preferred) of rather coarse zincpowder (say, about 10 mesh or coarser) are added, after the mixture hasbeen heated to vigorous boiling, in a flask or receptacle provided witha reflux condenser, and the boiling continued for a period of about 18hours.

During this operation, the zinc slowl dissolves, but a large proportionof the H. 1 component of the plnene hydrochlorid is evolved as a gas,and can be condensed or recovered for further use. This liberated acidcan be used to produce more pinene hydrochlorid for a succeeding run.

At the end of 18 hours this product will chlorid and less than 5 partsof resinous or:

high boiling point constituents, and not more than about 10 parts ofunconverted .pinene hydrochlorid. This mixtureis preferably separated byfractional distillation,

under reduced pressure, to separate the isobornyl acetate, camphene andcamphene h drochlorid mixture from the other ingre v ients,Whichmixture'can be subsequently converted into camphor in any knownway.

" The unconverted pinene hydrochlorid and the excess acetic acid arereturned to a suburing the carrymg out of the process as abovedescribed, somewhat less than the "total amount ofjzinc-employed, willbe dis- .solved axln other Words, metallic zinc'will be present duringthe entire procedure, while zinc chlorid will present, after theopjeration is started. 5 Zinc chlorid' is known. to be capable ofefl'ecting the isomerization of pinene hydrochlorid into isobornylcompounds, and also it has the effect of leading to the formation ofresinous or. high-boilingpoint products. The contact of the reactionmass, during the entire operation, with metallic zinc greatly reducesthe degree to which this undesirable secondary reaction proceeds,thereby producing both a better yield and a better product.

If an amount ofzinc is used substantially larger than above stated,there is produced a correspondingly larger amount of not only would theexcess thereof be uselessly consumed, but the yield of the threeproducts referred to (which in my process amounts to, say 80 or 85% ofthe theoretical) would be substantially reduced (say to 40-45%), alsothe hydrochloric acid would be practically all converted into zincchlorid,

and a much larger percentage of the resinous or high-boiling-pointderivatives would be produced.

It appears, from; my researches on this isomerization, that largequantities of zinc chlorid and high temperatures (120 C.) tend togreatly increase the amount of resinous products formed, while at lowtemperatures the degree of completeness of the isomerization drops offrapidly. That amount of. the resinification which is due to the hightemperature in the presence of a minimum effective quantity 0 ZnCl isaccordingly to be considered as a necessary evil. The stopping of theoperation at the end of about 18 hours (with the amount of zinc abovestated) also reduces the amount of the high-boiling-point or resinousproducts produced. If the process were continued for another fouror sixhours, the amount of pinene hydrochlorid left in the product wouldbeless, but the amount of the resinous byproducts would be enoughgreater to more than offset the greater degree of completion of thereaction.

In carrying out the process, the time of heating can be varied more orless. With about 2% of zinc 18 hours is generally suffici'ent; with lessthan this amount of zinc, or if the acid contains a little water, alonger time will be required. In general I boil the mixture until HClceases to be evolved,and for an hour or so longer.

Itwill be understood that glacial acetic acid is given as an instance ofthe fatty acids, and that. formic, propionic, stearic, etc., can beemployed, but since these aregenerally more expensive, the acetic ispreferred. Benzoic or salicylic acid can also be used. Likewise in placeof the pinene hydrochlorid, the compounds of other hydrohaloid acids (e.g. HBr and HF) can be used.

I claim:

1. A process of manufacturing an isobornyl ester and camphene mixture,which comprises heating together a mixture comprising a h drohaloid ofpinene and a carboxylic aci in the presence of an amount of zinccorresponding to not substantially more than 5% of the amount ofhydrohaloid of pinene.

2. A process of manufacturing an 150- bornyl ester and camphene mixture,which.

comprising maintainlng at a boiling temperature a mixture comprising a hdrohaloid of pinene and a carboxylic acid, in the presence of an amountof zinc corresponding to not substantially more than 5% of the amount ofhydrohaloid of pinene.

3. The process of transforming pinene hydrohaloid into an isobornylester and camphene mixture, which comprises heatin to the boiling pointa mixture of pinene hy rohaloid and a substantially anhydrous fattyacid, in the presence of about 2 to 3% of zinc in a form substantiallycoarser than zinc dust.

4. The herein described product comprising in addition to free fattyacid and zinc salts, not substantially less than parts of isobornylester of a fatty acid, about 10 parts of camphene and about-5 parts ofcamphene hydrohaloid, together with not substantially -more than 10parts of unconverted pinene hydrohaloid and not substantially more than5 parts of high boiling condensation products. I

5. The herein described product comprising, in addition to free fattyacid and zinc salt, about 83 to 85 parts of isobornyl ester of a fattyacid, about 10 parts of camphene and 5 parts of camphene hydrohaloid,together with a small quantity of unconverted pinene hydrohaloid and notsubstantiallymore than 5 parts of high boiling condensation products.

6. A- process of manufacturing an isobornyl ester and camphene mixture,which comprises heatin together a mixture comprising a hydroc 0nd ofpinene and a carboxylic acid, in the presence of an amount of zinccorresponding to not substantially more than 5% of the amount ofhydrochlorid of pinene.

7. The process of transforming pinene hydrohaloid into an isobornylester and camphene mixture, which comprises heatin to the boiling pointa mixture of pinene hy rohaloid and a substantially anhydrous fattyacid, in the presence of abou 2 to 3% of zinc.

8. A process of manufacturing an isobornyi ester and camphene mizrturewhich Lamas;

compries boiling together, for about 18 hours, a mixture comprising ahydrohaloid of pinene and a carboxylic acid, in the pres- 5 ence of-anamount of zinc correspond to about 2% of the amount of hydrohaloi ofpinene. 9. A process 0 f manufactm'ing an isop In testimon whereof Iaifix bornyl ester and eamphene mixture, which comprises heating toether a mixture com- 10 prislng a hydrohaloi of pinene and acetic acid,in the presence of an amount of zinc corresponding to not substantiallymore than 5% of the amount of hydrohaloid of pinene.

1W si ature. 15

AURENCE G. ON.

